1. Technical Field
This invention relates to the technology of attaching a wear resistant valve seat material to a light metal automotive engine head and more particularly to installing valve seat inserts rapidly and economically to aluminum cylinder heads.
2. Discussion of the Prior Art
Aluminum automobile cylinder heads are typically designed to receive pressed-in valve seat inserts of iron based material. The insert must be of substantial cross-sectional size to provide durability, strength and to retain the press fit. Optimal port geometry must be compromised leaving a smaller inside port diameter and cooling passage location, adjacent the seat, must be compromised Moreover, the greater size of the interface between the insert and cylinder head retards the cooling rate of the valve and seat area.
To eliminate pressed-in seat inserts, laser cladding of valve seats has been tried to obtain some increase in engine performance such as horsepower, torque and volumetric efficiency. Unfortunately laser cladding is an expensive technique that does not fit readily with traditional manufacturing facilities. Inertia welding of valve seats has also been tried in exotic applications for liquid metal breeder reactors where cost is not a factor; the insert (usually of chrome-cobalt-tungsten material) and a separate stainless steel weldment are attached to a rotary driver before inertially welding the weldment to a stainless steel valve seat. The same material is friction welded to the material (stainless steel to stainless steel). The driver is then machined away and the insert is shaped by machining (see U.S. Pat. No. 4,079,491). Obviously such technique is too costly and thermal conductivity, through layers of an insert and weldmerit to the head and coolant, is poor; the mass of the insert is too large to be effective for thermal conduction.